Rotor annulus for electric generator

ABSTRACT

A rotor annulus for an electric generator comprising an annular ring of magnetic members including permanent magnets and pole pieces arranged in respective end-to-end and circumaxial alternate series. A circular spring band surrounds the ring of members in pressing engagement with at least some of the members to hold all of the elements of the annulus in substantially fixed relationship with each other.

United States Patent Phelon [54] ROTOR ANNULUS FOR ELECTRIC GENERATOR[72] Inventor: Russell E. Phelon, Beverly Hills, Rio

Piedras, PR.

[22] Filed: Oct. 29, 1970 [21] App]. No.: 85,082

Related US. Application Data [62] Division of Ser. No. 824,138, May 13,1969, Pat. No.

521 U.S.Cl ..3l0/l5 6,3l0/261 [51] lnt.C|. ....ll02k 21/12 [58]FleldolSearch ..310/l56,42, 153, 49, 218, 310/261,262, 267,181, 185,187, 194, 192; g 29/596,598

[56] References Cited UNITED STATES PATENTS 2,417,195 3/1947 Hargreaves..310/42 us] 3,657,582 [451 Apr. 18, 1972 Primary Examiner-J. D. MillerAssistant ExaminerR. Skudy Attorney-McCormick, Pauling & Huber [57]ABSTRACT A rotor annulus for an electric generator comprising an annularring of magnetic members including permanent magnets and pole piecesarranged in respective end-to-end and circumaxial alternate series. Acircular spring band surrounds the ring of members in pressingengagement with at least some of the members to hold all of the elementsof the annulus in substantially fixed relationship with each other.

2 Claims, 10 Drawing Figures PAIENTEDAPR 18 19 22 3, 657. 582. SHEET 10F3 INVENTOR. RUSSELL E. PHELON M 'i a PATENTEMFR 18 I972 SHEET 2 BF 3FIG.7

PATENTEBAFR '18 m2 9.. 657, 582 sum 3 BF 3 FIG. 9 y

FIG. IO a K62 $2 CROSS REFERENCE This application is a division ofapplication Ser. No. 824,138, filed May 13, 1969, now a U.S. Pat. No.3,538,394 and entitled Rotor Annulus for Electric Generator."

A rotor annulus similar in some respects to the annulus hereinafterdescribed is shown in my U.S. Pat. No. 3,132,270, issued May 5, 1964,and entitled Rotor Annulus for Electric Generator."

BACKGROUND OF THE INVENTION The invention relates generally to electricgenerators adapted for use with internal combustion engines and moreparticularly to a rotor for an electric generator of the flywheel typein which a plurality of permanent magnets and associated pole pieces areembedded in the inner peripheral portions of the rim of the flywheel.

The manufacture of such rotors requires that individual magnets and polepieces first be assembled to form an annulus having a large centralopening. Subsequently, the annulus is inserted in a casting die having adie cavity conforming to the required shape of the rotor andnon-magnetic metal is cast around the major portion of the annulus toform the rotor flywheel.

Heretofore, and in accordance with my aforementioned U.S. Pat. No.3,132,270, an annulus has been formed comprising an annular series ofmagnetic members including pole pieces and magnets surrounded by acircular band. One or more spacing members or shims each insertedbetween two of the magnetic members tend to enlarge the diameter of theannular series of magnetic members and thereby press some of the membersradially outwardly against the circular band so as to hold all membersof the annulus in substantially fixed relationship with each other. Thismethod of manufacture is disadvantageous in that it requires positioningone or more spacers otherwise unessential in the assembly and may andprobably does result in a slightly eliptical or otherwise out of roundannulus which may require correction for any deviation from a truecircular shape prior to the casting step.

Accordingly, the general aim of this invention is to provide an improvedannulus of magnets and pole pieces for use in the manufacture of a rotorfor an electric generator, such annulus being readily and easily formedinto a self-sustaining unit prior to its placement in the die cavitywithout the expenditure of much time or labor in accurately positioningor securing the parts relative to each other.

SUMMARY OF THE INVENTION In accordance with the present invention, anannulus is provided which comprises a plurality of magnetic membersincluding magnets and pole pieces positioned relative to each other toform an annular ring having a central opening of circular shape. Acircular circumaxially expandable spring member surrounds the ring inpressing engagement with at least some of the magnetic members to holdthe various elements ofthe annulus in assembly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a castrotor for an electric generator and having an annulus made in accordancewith the present invention.

FIG. 2 is a perspective view of a fixture on which the annulus of FIG. 1is assembled.

FIG. 3 is a perspective view of one of the pieces included in theannulus of FIG. 1.

FIG. 4 is a perspective view of one of the magnets included in theannulus of FIG. -1.

FIG. 5 is a plan view of a partially assembled annulus and shows theannulus prior to deformation of its hand and a tool positioned fordeforming the band.

FIG. 6 is a plan view of an assembled annulus.

FIG. 7 is a side view ofthe annulus ofFIG. 6.

laminated pole FIG. 8 is a perspective view of another circular bandused in making another annulus in accordance with the present invention.I

FIG. 9 is a side view of another partially assembled annulus and showsthe band of FIG. 8 in its preassembled condition.

FIG. 10 is a side view of the assembled annulus of FIG. 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS An annulus made inaccordance with the present invention has a large central opening andcomprises an annular series of magnetic members which series includes anannular arrangement of permanent magnets and also includes an annulararrangement of pole pieces. The pole pieces respectively engage themagnets and have their inner faces at least approximately tangent to acentral cylindrical surface which has a diameter approximately the sameas that of said large central opening. The annulus also includes acircular band which surrounds said magnetic members and engages at leastsome of the members and to apply continuing radial pressure to thelatter members to hold all of the elements of the annulus insubstantially fixed relationship with each other. After the annulus hasbeen formed, it is inserted in a casting die and a non-magnetic materialis cast about its major portion so as to form the body of a rotorstructure such as indicated at 10 in FIG. 1 which has a large centralopening 12.

One example of an annulus of permanent magnets and pole piecesconstructed in accordance with the present invention is indicatedgenerally at 14 in F [Os 6 and 7. The annulus 14 comprises tangentiallycharged magnets 16, 16 with pole pieces 18, 18 associated therewithinterposed between them. A resilient circular band 20'circumaxiallysurrounds the ring of members which comprises the magnets and polepieces and holds them in assembled relation with each other in a mannerhereinafter described. As shown, the several magnets and pole pieces ofthe annulus are alternately positioned with respect to each other butthe invention in its broader aspects is not limited to the particulararrangement shown.

The permanent magnets 16, 16 which are utilized in the annulus 14 may beindividually formed or may if desired, be cast in a continuous stripprovided with weakening grooves which permit the strip to be broken toobtain individual magnets. For a disclosure of this strip casting methodof providing magnets, reference may be had to my aforementioned U.S.patentEach magnet 16 has a generally rectangular shape and includessmooth opposite end surfaces 22, 22, a substantially flat inner surface24 and a generally arcuately shaped outer surface 26 as best shown inFIG. 4. When the magnets 16, 16 are changed tangentially, the polepieces 18, 18 may advantageously be formed generally arcuate in shapewith curved inner faces 28, 28 each having a radius of curvaturesubstantially equal to that of the central opening 12. Each pole piece18, 18 is a lamination of a plurality of thin metal plates 30, 30secured together by rivets 32, 32 and best shown in FIG. 3.

Preferably and as shown, the pole pieces l8, 18 are formed in pairs,each pair being joined together by an integral connection portion 34spaced radially inwardly of the pole faces 28, 28. The combined two-partpole pieces are sometimes hereinafter referred to as duplex pole pieces.When there are pairs of pole pieces, each pair has an intermediatemagnet receiving recess 36, the inner side surfaces 38, 38 of which areshaped to complement the smooth opposite side surfaces 22, 22 of themagnets l6, 16. The inner surface 39 of each recess 36 is cut away toprovide a clearance space between the bottom surface 24 of an associatedmagnet 16 and the pole pieces 18 so that the surface 24 will not preventproper location of the magnet 16 in the recesses. In a similar manner,end portions 40, 40 of the plates 30, 30 are shaped to define one-halfof a recess 42 similar to the intermediate recess 36so that the oppositeend portions 40, 40 of adjacent pairs of pole pieces will cooperate todefine magnet receiving recesses 42, 42 between adjacent pairs of polepieces 18, 18.

In the particular annulus construction shown in the drawings, sixmagnets are utilized and are positioned in the recesses 42, 42 formed bythe end portions 40, 40 of adjacent duplex pole pieces, magnets beingomitted in the recesses 36, 36. It will be evident, however, thatmagnets may, if desired, be positioned in the latter recesses. Themagnets 16, 16 and the pole pieces l8, 18 are thus arranged in anannular series and the several pole pieces and magnets are alternatelypositioned with respect to each other.

The band 20 in its preassembled condition has an inside diameter greaterthan the outside diameter of the ring of members and may be made fromany suitable material, but preferably and as shown it is made from anendless piece of resilient wire. If steel wire is used to make the bandrather than a more expensive non-magnetic material, it is preferablethat wire of a relatively light guage be used to minimize any tendencyof the band to short circuit the magnets 16, 16. The ends of the bandsmay be secured together by any suitable fastening means and may, forexample, be joined by spot weldmg.

The annulus 14 is preferably assembled on a fixture, such a fixturebeing indicated generally at 44 in FIG. 2. The fixture 44 has a base 46and a generally cylindrical portion 48, the diameter of which issubstantially equal to the diameter of the central opening 12. Acircumaxially spaced series of recesses 50, 50 formed in the centralportion 48 each respectively received and complement an associatedconnecting portion 34 of a duplex pole piece. Thus, the recesses 50, 50aid in locating or positioning the pole pieces with respect to thefixture 44. When the various magnet members have been positioned on thefixture 44 to form an annular ring of members, as aforedescribed, theband 20 is positioned to circumaxially surround the ring of members inthe manner generally shown in FIG. 5. Thereafter, at least one portionof the band is deformed to reduce the diameter thereof and bring theband into pressing engagement with at least some of the magnetic membersto hold all of the elements of the annulus in substantially fixedrelationship with each other. In accordance with one presently preferredmethod of practicing the invention, a portion of the band 20 is deformedby applying a twisting force thereto as by grasping it between two jawssuch as the jaws of the pliers 52 shown in FIG. and rotating the jawsabout an axis extending radially of the annulus 14. The band 20 in itsdeformed state has at least one non-circumferential or axially off-setportion such as indicated at 53 and best shown in FIG. 7.

The formation of the rotor is completed by positioning the annulus 14 inthe cavity of a casting die (not shown) and casting non-magneticmaterial such as aluminum around the major portion of the annulus 14.After the casting is removed from the die cavity and has cooledsufficiently, the inner surfaces 28, 28 of the pole pieces 18, 18 aremachined so as to make them truly cylindrical. In the machining process,the connecting portions 34, 34 are machined away and the pole pieces 18,18 of each duplex pole piece are thereby separated.

Considering now FIGS. 8-10, another annulus made in accordance with thepresent invention is shown in FIG. 10 and indicated generally by thereference numeral 14a. The annulus 14a is substantially identical inmany respects to the annulus 14 and parts identical to parts previouslydescribed bear the same reference numeral and a letter a suffix and willnot be hereinafter further described. The annulus 14a comprises a ringof members which include magnets 16a, 16a and pole pieces 18a, 18acircumaxially surrounded and retained in assembly by a resilientcircular band. The band may be made of various materials and may takevarious forms, but in accordance with one presently preferred method forpracticing the invention, the band comprises a tension spring 2011formed from coiled spring metal and adapted to be circumferentiallyexpanded or stretched radially outwardly to enlarge its inside diameter.

The annulus 14a is preferably assembled on a fixture such as the fixture44 previously described. The band 20a in its relaxed condition has aninside diameter somewhat smaller than the outside diameter of the ringof members 16a, 16a and 18a, 18a. In its preassembled condition,however, the band 20a has an inside diameter greater than the outsidediameter of the ring of members. A radially outwardly directedstretching force is applied to the band 20a to bring the band to itspreassembled condition. Thereafter, the band is positioned tocircumaxially surround the ring of members in the manner generally shownin FIG. 10. The stretching force is then released whereupon the bandcontracts into pressing engagement with at least some of the members tohold all of the elements of the annulus in substantially fixedrelationship with each other. The operations for forming a rotor whichincludes the annulus 14a are substantially identical to those previouslydescribed with reference to formation of the rotor 10.

Iclaim:

1. An annulus for the rotor of an electric generator, which annulus hasa large central opening and comprises in combination: an annular seriesof magnetic members which series includes an annular arrangement ofpermanent magnets and also includes an annular arrangement of polepieces respectively engaging the magnets and located with theirinterfaces approximately tangent to a cylindrical surface having thediameter of said large central opening, and a generally circularcircumferentially expandable coil spring surrounding said.

magnetic members and in pressure engagement with at least some of saidmembers holding all of the elements of the annulus in substantiallyfixed relationship with each other.

2. An annulus for the rotor of an electric generator as set forth inclaim 1 wherein said coil spring is made of magnetic material.

Dated April 18,

Patent No. 3 ,657, 582

Russell E.

Phelon Inventor(s) tified patent It is certified that error appears inthe above-iden and that said Letters Patent are hereby corrected asshown below:

Col, 1, line 2, "3,538,394" should read --3,58l,394-. Col 3, line28,"received" should read -receive- Signed and sealed this 12th day ofSeptember 1972.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M .FLETCHER,JR. Attesting Officer Commissionerof Patents F"? FTY-( P T 1 1m in nn xo p v CL i ii lcA ii 13 U1 bQfiitbbLOU Patent No. 3 ,657, 582 Date April 18, 1972 Inventor s Russell E.Phelon It is certified that error appears in the above identified patentand that said Letters Patent are hereby corrected as shown below:

Col, 1, line 2, "3,538,394" should read --3,5s1,394 Col. 3, line28,"received" should read --receive- Signed and sealed this 12th day ofSeptember 1972.

(SEAL) Attest ROBERT GOTTSCHALK Commissioner of Patents EDWARDM.FLETCHER,JR. Attesting Officer

1. An annulus for the rotor of an electric generator, which annulus hasa large central opening and comprises in combination: an annular seriesof magnetic members which series includes an annular arrangement ofpermanent magnets and also includes an annular arrangement of polepieces respectively engaging the magnets and located with theirinterfaces approximately tangent to a cylindrical surface having thediameter of said large central opening, and a generally circularcircumferentially expandable coil spring surrounding said magneticmembers and in pressure engagement with at least some of said membersholding all of the elements of the annulus in substantially fixedrelationship with each other.
 2. An annulus for the rotor of an electricgenerator as set forth in claim 1 wherein said coil spring is made ofmagnetic material.